Nervous System & neurons & synaptic transmission

Question 1

What is the nervous system?

Answer 1

A specialised network of cells in the human body and is our primary internal communication system.

Question 2

The 2 main functions of the nervous system:

Answer 2

To collect, process, and respond to information in the environment.
To coordinate the working of different organs and cells in the body.

Question 3

The sub-divisions of the nervous system:

Answer 3

Central nervous system (CNS) and Peripheral nervous system (PNS)

Question 4

The central nervous system (CNS)

Answer 4

Made up of the brain and spinal cord, which passes messages to and from the brain and connects nerves to the PNS.

Question 5

Brain.

Answer 5

Centre of all conscious awareness.

Divided into hemispheres.

Question 6

Spinal cord.

Answer 6

Extension of the brain.

Responsible for reflex actions.

Question 7

The cerebral cortex is…

Answer 7

highly developed in humans and is what distinguishes our higher mental functions from those of animals.

Question 8

The peripheral nervous system (PNS)

Answer 8

Sends information to the CNS from the environment and transmits messages from CNS to muscles and glands in the body.

Question 9

The subdivisions of PNS:

Answer 9

Autonomic Nervous system (ANS).

Somatic Nervous system (SNS).

Question 10

ANS.

Answer 10

Governs vital functions in the body such as breathing, heart rate, digestion, sexual arousal, and stress responses.

Question 11

SNS.

Answer 11

Controls - voluntary - muscle movement and receives information from sensory receptors.

Question 12

Neurons.

Answer 12

Nerve cells that process and transmit messages through electrical and chemical signals.

Question 13

Types of neurons.

Answer 13

Sensory neurons, relay neurons, motor neurons.

Question 14

Sensory neurons.

Answer 14

Carry messages from PNS to CNS.

Long dendrites and short axons.

Question 15

Relay neurons.

Answer 15

Connect the sensory and motor neurons.

Short dendrites and short axons.

Question 16

Motor neurons.

Answer 16

Connect the CNS to effectors such as muscles and glands.

Short dendrites and long axons.

Question 17

Neurons vary in size from…

Answer 17

Less than a millimetre to up to a metre long, but all share the same basic structure.

Question 18

Cell (soma) body.

Answer 18

Includes a nucleus, containing the genetic material of the cell.

Question 19

Dendrites.

Answer 19

Branch-like structures protrude from the cell body, which carries nerve impulses from neighbouring neurons towards the cell body.

Question 20

Axon.

Answer 20

Carries the impulses away from the cell body down the length of the neuron; covered in a fatty layer of the myelin sheath protecting the axon and speeds up the electrical transmission of the impulse.

Question 21

Nodes of Ranvier.

Answer 21

The gaps between the myelin sheath.

Speeds up the transmission of the impulse by forcing it to ‘jump’ across the gaps along the axon.

Question 22

Terminal buttons.

Answer 22

At the end of the axon that communicates with the next neuron in the chain across a gap known as the synapse.

Question 23

What is meant by electric transmission?

Answer 23

Firing of a neuron.

Question 24

What happens when the neuron is in a resting state?

Answer 24

The inside of the cell will be negatively charged compared to the outside of the cell.

Question 25

What happens when a neuron is activated by a stimulus?

Answer 25

The inside of the cell becomes positively charged for a split second causing action potential to occur. Creating an electrical impulse to travel down the axon towards the end of the neuron.

Question 26

Synaptic transmission

Answer 26

Process by which neighbouring neurons communicate with each other by sending chemical messages across the synaptic cleft.

Question 27

Neurotransmitter

Answer 27

Brain chemicals are released from synaptic vesicles that relay signals across the synapse from one neuron to another. Can be broadly divided into those that perform an excitatory function and those that perform an inhibitory function.

Question 28

Neural networks

Answer 28

Neurons communicate with each other within groups.

Question 29

How are neurons separated?

Answer 29

By a synapse.

Question 30

Signals within neurons are...

Answer 30

transmitted electrically.

Question 31

Signals between neurons are...

Answer 31

transmitted chemically.

Question 32

End of a neuron is called...

Answer 32

the presynaptic terminal.

Question 33

When the electrical impulse reaches the end of the neuron...

Answer 33

it triggers the release of neurotransmitter from tiny sacs called synaptic vesicles.

Question 34

Once the neurotransmitter crosses the gap...

Answer 34

it is taken up by the postsynaptic receptor sites (dendrites).

Question 35

What happens at the postsynaptic receptor sites?

Answer 35

The chemical message is converted back into an electrical impulse and the process of transmission begins again in this other neuron.

Question 36

Why does each neurotransmitter have its own specific molecular structure?

Answer 36

To fit perfectly into a post-synaptic receptor site.

Question 37

What effects can a neurotransmitter have on a neighbouring neuron?

Answer 37

Excitatory or inhibitory effect.

Question 38

Excitation.

Answer 38

When a neurotransmitter increases the positive charge of the postsynaptic neuron. This increases the likelihood that the neuron will fire and pass on the electrical impulse.

Question 39

Inhibition.

Answer 39

When a neurotransmitter makes the charge of the postsynaptic neuron more negative. This decreases the likelihood that the neuron will fire and pass on the electrical impulse.

Question 40

Summation

Answer 40

Whether a postsynaptic neuron does fire is decided by this process.

Question 41

If the net effect on the postsynaptic neuron is inhibitory...

Answer 41

the postsynaptic neuron is less likely to fire.

Question 42

If the net effect is excitatory...

Answer 42

the inside of the postsynaptic neuron becomes positively charged.

Question 43

Once the electrical impulse is created...

Answer 43

it travels down the neuron.

Question 44

Summation - therefore the action potential of the postsynaptic neuron is only triggered...

Answer 44

if the sum of the excitatory or inhibitory signals at any one time reaches the threshold.